CHAPTER 5 RESULTS OF PILOT INVENTORY SURVEY

The Study on Risk Management for Sediment-Related Disaster on Final Report Volume II Selected National Highways in the Republic of the Philippines Main Report

NIPPON KOEI CO., LTD. June 2007

OYO INTERNATIONAL CORPORATION

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CHAPTER 5

RESULTS OF PILOT INVENTORY SURVEY

5.1 Results of Preliminary Inventory Survey

5.1.1 Selection of Road Sections for PIS

The Road Sections to be surveyed were selected before the conduct of the PIS (Stage I) based on the information from the preparatory study, the initial field reconnaissance survey conducted by the Study Team together with the Counterpart Team from the 4th to the 12th of April 2006 and suggestions from the DPWH. Selected Road Sections for PIS are listed in Table 5.1.

The selection of Road Sections for the Inventory Survey was carried out considering the following criteria:

1) Security in the area,

2) Accessibility;

3) Coverage of all kinds of disaster types;

4) Equitable regional distribution;

5) Suggestions from DPWH; and

6) Present condition of the road.




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Table 5.1 Road Sections Selected for the Preliminary Inventory Survey

Region Road Section Section

(km) Length

(km) DEO in Charge

Road Classification

AADT Disaster

Types

241-244 3 Baguio City Kennon Rd

214-241 27 Benguet 1st

S 6,880/ 5,014

RS, RC, RE, SC, DF

Baguio- Bontoc Rd (Halsema Highway) 263-341 78 Benguet 2nd

A(OT) 953 RS, SC, RC, DF, LS

Nueva Vizcaya- Ifugao-Mt Province Rd (Lagawe- Banaue)

301-333 32 Ifugao

S 275/ 3,116 SC, RS,

DF, RC, LS

CAR

Subtotal Length(km) 140 Daang Maharlika (LZ) (Dalton Pass)

208-220 12 Nueva Vizcaya Sub

A(NS) 3,769 RS, SC, RC, DF, RE II

Subtotal Length(km) 12 5-30 25 Cebu City Cebu- Balamban

Transcentral 30-42 12 Cebu 3rd A(EW) 1,001/

1,305 RS, SC, RC, DF

Toledo-Baliri- Santander Rd (Ginatilan- Alegria)

143-179 36 Cebu 4th A(NS) 500/

12,000

CE, RC, RE, SC, RS

VII

Subtotal Length(km) 73 Wright-Taft-Borongan Rd 843-859 16 Samar 2nd A(EW) 500/

1,374 RS, SC, RC, DF

995-1003 8 Leyte 5th Daang Maharlika (LT) (Mahaplag- Sugod) 1003- 1018 15 Southern

Leyte

A(NS)

659/ 1,581

RS, SC, RC, DF, RE, LS

VIII

Subtotal Length(km) 39 Misamis Oriental- Bukidnon-Agusan Road

1428-1464 36 Bukidnon 3rd

A(NS) 3,421 RS, SC, RC

Bukidnon-Davao City Rd 1605-1607 2 Bukidnon

2nd A(NS) 3,340 SC, RS,

RC

X

Subtotal Length (km) 38

Davao-Cotabato Road 1525-1555 30 Davao-Del Sur 1st

A(NS) 3,486/ 6,517

RE, RS, SC XI

Subtotal Length (km) 30 Total Length (km) 332

Disaster Types; SC: Soils Slope Collapse; RC: Rock Slope Collapse; LS: Landslide; RS: Road Slip; DF: Debris Flow; RE: River Erosion; CE: Coastal Erosion; In each Road Section, the disaster type is listed in the order of dominance Road Classification; A(NS) Arterial (North-South Backbone), A(EW): Arterial (East-West Lateral), A(OT): Arterial (Other Road of Strategic Importance), S: Secondary National Road,

5.1.2 Result of Preliminary Inventory Survey

Sixteen National Highway road sections in six Regions were selected for the pilot PIS. A total length of 332 km had been surveyed by mid-January 2007.

Along the 332 km of road sections, 1933 slopes were surveyed based on the PIS Criteria.




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Results indicate that around 61% of the slopes had a high risk level that required a DIS. The distribution of the disaster types and number of slopes in the PIS and the DIS are shown in Table 5.2. A summary of the PIS results is shown in Table 5.3 and Figure 5.4.

Table 5.2 Distribution of Disaster Types in PIS Sections

Disaster Type PIS Slopes Selected DIS Slopes

Soil Slope Collapse 533 (28%) 387 (73% of PIS)

Rock Slope Collapse 301 (16%) 268 (89% of PIS)

Landslides 8 (0%) 8 (100% of PIS)

Road Slips 784 (41%) 334 (44% of PIS)

Debris Flow 147 (8%) 60 (41% of PIS)

River Erosion 84 (4%) 46 (55% of PIS)

Costal Erosion 76 (4%) 58 (76% of PIS)

Total 1933 (100%) 1170 (61% of PIS)

Source: PIS results for the 332 km of sections surveyed in 16 selected road sections.

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Table 5.3 PIS Result of Study Road Sections




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Figure 5.1 Nos. of PIS Slopes/Selected DIS Slopes of Pilot Inventory Survey

5.1.3 Results of the PIS by Region

(1) Cordillera Autonomous Region (CAR) Three roads in CAR were included in this study. Those were Kennon Road, Baguio-Bontoc Road (Halsema Highway) and Nueva Vizcaya-Ifugao-Mt Province Road (Lagawe-Banaue Road). Those three roads mostly traverse the steep slopes of valleys and ridges in the mountainous areas of the Cordillera Region, and are therefore prone to road slope and sediment-related disasters.

Kennon Road is being managed by two District Offices of DPWH, namely; Baguio City DEO (km 241 to km 244 for PIS) and Benguet 1st DEO (km 241 to km 244 for PIS). The Nueva Vizcaya-Ifugao-Mt. Province Road (Lagawe-Banaue Road) is managed by the Ifugao DEO, and the Baguio-Bontoc Road (Halsema Highway) is managed by the Benguet 2nd DEO (km 263 to km 341 for PIS).

(a) Kennon Road A total of 216 slopes along 30 km of road sections were surveyed along Kennon Road.

The percentages for the various disaster types were: 41% Road Slip; 25% Rock Slope Collapse; 16% River Erosion; 14% Soil Slope Collapse; and 4% Debris Flow. Around 55% of the PIS slopes were judged to require a DIS. The PIS Results along Kennon Road are shown in Figures 5.2 and 5.4

Nos

. of S

lope

s 533

387

301268

8 8

784

343

147

6084

4676

58

0

100

200

300

400

500

600

700

800

SC RC LS RS DF RE CE

Preliminary Inventory Survey

Detailed Inventory Survey

Disaster Type




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(b) Baguio Bontoc Rd (Halsema Highway) A total of 386 slopes were surveyed along the Baguio Bontoc Rd, with the following percentages for each disaster type: 40% Road Slip, 32% Soil Slope Collapse, 20% Rock Slope Collapse, 8% Debris Flow, 11% Rock Slope Collapse and 1 % Landslide. Around 66% of the slopes in the PIS will be subjected to DIS.

The PIS results along the Baguio-Bontoc Rd are shown in Figures 5.3 and 5.5.

(c) Nueva Vizcaya-Ifugao-Mt. Province Road (Lagawe-Banaue Road) A total of 245 slopes were surveyed along the Nueva Vizcaya-Ifugao-Mt. Province Road, with the following percentages for each disaster type: 37% Soil Collapse; 29% Road Slip, 22% Debris Flow, 10% Rock Slope Collapse and 2 % Landslide. In this road section, about 56% of the slopes in the PIS will be subjected to DIS.

The PIS results along the Nueva Vizcaya-Ifugao-Mt. Province Road are shown in Figure 5.6.

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Figure 5.2 PIS Results Profile for Kennon Road

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Figure 5.3 PIS Results Profile for Baguio –Bontoc Road(Halsema Highway)


NIPPON KOEI CO., LTD. 5-9 June 2007


Figure 5.4 PIS Results for Kennon Road

Figure 5.5 PIS Results for Baguio Bontoc Road (Halsema Highway)

Figure 5.6 PIS Results for Nueva Vizcaya – Ifugao - Mt. Province Road

31

15

5451

0 0

88

27

95

34

20

0 00

10

20

30

40

50

60

70

80

90


Preliminary Inventory Survey Detailed Inventory Survey

DISASTER TYPE

NO. O

F SU

RVEY

SIT

E

125

113

7670

2 2

153

116

30

17

0 0 0 00

20

40

60

80

100

120

140

160



DISASTER TYPE

NO. O

F SU

RVEY

SIT

E

91

72

24 22

4 4

72

22

54

18

0 0 0 00102030405060708090

100



NO. O

F SU

RVEY

SIT

E

Num

ber

of S

urve

y Sl

ope




(2) Region II The section of the Daang Maharlika (LZ) (km 208+000 to km 220+000) was surveyed.

(a) Daang Maharlika (LZ) (Dalton Pass) A total of 118 slopes along a road length of 12 km (km 208+000 to km 220+000) were surveyed along Daang Maharlika (LZ). Of these, 31% were Road Slips; 26% Soil Slope Collapse; 23% Rock Slope Collapse; 14% Debris Flow; and the remaining 5% River Erosion. Around 42% of the PIS slopes meet the DIS selection criteria. The PIS result along Daang Maharlika (LZ) is shown in Figures 5.7. and 5.8.

Figure 5.7 PIS Results for Daang Maharlika (LZ)

31

11

27

23

0 0

37

9

17

56

20 00

5

10

15

20

25

30

35

40



DISASTER TYPE

NO. O

F SU

RVEY

SIT

EN

umbe

r of

Sur

vey

Slop

e

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150

170

190

210

230

250

270

290

310

330

350

370

390

410

430

450

470

49020

8+00

0

209+

000

210+

000

211+

000

212+

000

213+

000

214+

000

215+

000

216+

000

217+

000

218+

000

219+

000

220+

000

KM. STATION

ELEV

ATI

ON

(m)

DF DF-DIS

RC RC-DIS

RE RE-DIS

RS RS-DIS

SC SC-DIS

ROAD

Figure 5.8 PIS Results Profile for Daang Maharlika (LZ)




(3) Region VII Two Road Sections were surveyed in the PIS for Region VII, namely: Cebu Balamban Transcentral Highway and the Ginatilan Alegria Section of Toledo-Baliri-Santander Rd. The former is under the management of and maintained by two DEOs, the Cebu City DEO (km 5 to km 30) and Cebu 3rd DEO (km 30 to km 42) and the later is under the Cebu 4th DEO.

(a) Cebu-Balamban Transcentral Highway The Cebu-Balamban Transcentral Highway traverses the mountainous area of Cebu province with a total of 279 sub-sections meeting the PIS criteria. The disaster types observed were Road Slips (55%); Soil Slope Collapse (28%); Rock Slope Collapse (13%); and Debris Flow (4%). Considering the present conditions along this route, around 45% qualify for DIS.

The PIS results of the Cebu-Balamban Transcentral Highway are shown in Figure 5.9.

(b) Ginatilan Alegria Section of Toledo-Baliri-Santander Rd The total length of surveyed sections along Ginatilan Alegria Section of Toledo-Baliri-Santander Rd is 36 km, starting from km 143 to km 179. The most common disaster type was Coastal Erosion (62%) caused by tidal action. The remaining 38% is distributed into combinations of Soil Slope Collapse, Rock Slope Collapse and River Erosion. Around 72% of PIS slopes require a DIS.

The PIS results along Ginatilan Alegria Section are shown in Figure 5.10.




Figure 5.9 PIS results for Cebu-Balamban Transcentral Highway

Km5

Km40

Km30 Km25

Km20

Km15

Km10

Km35

CEBU-BALAMBAN TRANSCENTRAL HIGHWAY

80

36

152

011

0

279

5135

97

0 7 0 0

190

0

25

50

75

100

125

150

175

200

225

250

275

300

SC RC LS RS DF RE CE Total

DISASTER TYPE

NO. O

F SU

RVEY

SIT

E

Preliminary Inventory SurveyDetailed Inventory Survey

PIS study route

Km5+000

Km42+000

80

4539

35

0 0

160

44

116

0 0 0 00

20

40

60

80

100

120

140

160


DISASTER TYPE

NO. O

F SU

RVE

Y S

ITE

PIS

DIS

Soil Slope Collapse

Soil Slope Collapse (DIS is required)

Rock Slope Collapse

Rock Slope Collapse (DIS is required)

Road Slip

Road Slip (DIS is required)

Debris Flow

Debris Flow (DIS is required)

Num

ber

of S

urve

y Sl

ope




Figure 5.10 PIS Results along Ginatilan - Alegria Section of Toledo-Baliri-Santander Road




(4) Region VIII

There are two Road Sections for Pilot PIS in Region VIII, namely: the Wright-Taft-Borongan Road, which is under the responsibility of the Samar 2nd DEO; and the Mahaplag-Sugod Section of Daang Maharlika (LT) under the Leyte 5th DEO and Southern Leyte DEO.

(a) Wright - Taft - Borongan Rd PIS in Wright-Taft road started at km 843+000 and ended at km 859+000.

A total of 65 slopes were surveyed along the Wright-Taft-Borongan Road, which traverses a mountainous area. The disaster types observed were: 52% Road Slips; 28%, Soil Slope Collapse; 14% Rock Slope Collapse; and 6% Debris Flow. About 55% of the 65 PIS slopes conform to the DIS criteria.

The PIS results for Wright- Taft- Borongan Rd are shown in Figure 5.11.

(b) Daang Maharlika (LT) (Mahaplag-Sugod Section) Daang Maharlika (LT) (Mahaplag - Sugod Section) from km 995 – km 1003 under the Leyte 5th DEO and from km 1103 – km 1018 under Southern Leyte DEO was surveyed.

The Daang Maharlika Highway(LT) (Mahaplag-Sugod Section) traverses the steep slopes of a mountainous area, and 162 slopes were surveyed. The two most common disaster types observed were Road Slips (40%) and Soil Slope Collapse (38%). Other types were Rock Slope Collapse (11%); Debris Flow (6%); River Erosion (5%); and Landslides (1%). Out of the 162 slopes surveyed, 60% of qualify for the conduct of a DIS.

The PIS results of the Daang Maharlika Highway (LT) (Mahaplag-Sugod Road) are shown in Figure 5.12.

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Figure 5.11 PIS Results for Wright-Taft-Borongan Road


NIPPON KOEI CO., LTD. 5 - 17 June 2007


MAHAPLAG-SOGOD ROAD

162

01010

2

61

18

61

155

01010

2

57

18

58

0

25

50

75

100

125

150

175

SC RC LS RS DF RE CE Total

DISASTER TYPE

NO. O

F S

URV

EY S

ITE

Preliminary Inventory SurveyDetailed Inventory Survey

Km990

Km995

Km1000

km 1005

Km 1010

Km 1015

PIS study Road

Km 1018

Km995

^

Figure 5.12 PIS Results for Daang Maharlika Highway (LT) (Mahaplag-Sugod Section)

61

42

18 18

2 2

64

26

97 8

5

0 00

10

20

30

40

50

60

70


DISASTER TYPE

NO

. OF

SUR

VEY

SIT

E

Soil Slope Collapse

Soil Slope Collapse (DIS is required)

Rock Slope Collapse

Rock Slope Collapse (DIS is required)

Road Slip

Road Slip (DIS is required)

River Erosion

River Erosion (DIS is required)

Debris Flow

Debris Flow (DIS is required)




6960

20 18

0 0

157

71

1 0 1 0 0 00

20

40

60

80

100

120

140

160



DISASTER TYPE

NO. O

F SU

RVEY

SIT

E(5) Region X

The original scope of this study did not include any Road Sections in Mindanao. However, with the strong recommendation of the DPWH, the Study Team added two Road Sections for Region X as pilot survey sections and one route for Region XI. The Region X routes were Sayre Highway (Misamis Oriental-Bukidnon-Agusan Road) and the Bukidnon-Davao City Road.

The PIS was undertaken jointly by the Central Office (CO) counterpart personnel and the field engineers from Bukidnon's 2nd and 3rd DEOs. The surveyed section starts from km 1427+717 and runs to km 1463+500 traversing mostly mountainous areas. The surveyed section of Bukidnon–Davao City Road, which starts at km 1605+685 and runs to km 1607+000, was also undertaken jointly by CO counterpart personnel and DEO representatives and was found to have terrain characteristics similar to the Sayre Highway.

(a) Sayre Highway (Misamis Oriental-Bukidnon-Agusan Road) Sayre Highway has a total of 248 slopes meeting the PIS criteria. The disaster types observed are Road Slips (63%); Soil Slope Collapse (28%); Rock Slope Collapse (8%); and River Erosion (0%). A total of 72% of those PIS slopes require DIS.

PIS results for Sayre Highway are shown in Figure 5.13.

Figure 5.13 PIS Result for Sayre Highway (Misamis Oriental-Bukidnon-Agusan Road)

(b) Bukidnon-Davao City Road Along this road, nine slopes were surveyed, and the prevalent disaster types observed were Soil Slope Collapse (67%); Road Slips (22%); and Rock Slope Collapse (11%). Results




show that all of the slopes need to be included in the DIS.

The PIS results for the Bukidnon-Davao City Road are shown in Figure 5.14.

Figure 5.14 PIS Result for Bukidnon-Davao City Road

(6) Region XI

The route identified for Region XI was the Davao-Cotabato road from km 1525 to km 1555. During the survey headed by the Davao del Sur DEO, it was found that most of the route traverses flat terrain with agricultural plantations. However, 27 slopes were identified during the PIS.

(a) Davao - Cotabato Road The disaster types observed were River Erosion (78%); Road Slips (15%); and Soil Slope Collapse (7%), of which, 60% of the PIS slopes require DIS.

The PIS results for the Davao-Cotabato Road are shown in Figure 5.15.

Figure 5.15 PIS Result for Davao-Cotabato Road

6 6

1 1

0 0

2 2

0 0 0 0 0 00

1

2

3

4

5

6


NO. O

F SU

RVEY

SIT

E

2 2

0 0 0 0

4

2

0 0

21

12

0 00

5

10

15

20

25



DISASTER TYPE

NO. O

F SU

RVE

Y SI

TE




5.2 Result of Detailed Inventory Survey

5.2.1 Selection of Road Sections for DIS

Road Sections surveyed for the DIS were selected from the PIS Road Sections according to the criteria listed in Table 5.4. Selection flow is shown in Figure 5.16.

Road sections from Regions X and XI were added to the original 50 km stipulated in the Inception Report, as recommended and executed by DPWH officials and local counterparts.

Table 5.4 Criteria for Selection of Detailed Inventory Survey Sections Primary Criteria 1) Equitable Regional Distribution At least one section will be selected in CAR, Region II

and Region VII, Region VIII-Samar Region VIII-Leyte, Region X, and Region XI (Minimum length per region is 3 km)

Secondary Criteria

2) To be Conducted by Many Responsible DEOs

All concerned DEOs conducting Preliminary inventory surveys will be selected Minimum section is 3 km and max length section is 10 km

Tertiary Criteria

3) Priority sections recommended by RO/DEO

Potential frequency of road slope disasters is high Disasters have occurred in the past Visible disturbances are recognized

4) Disaster type Most of disaster types shall be surveyed on each section All of the disaster types shall be surveyed

Figure 5.16 Selection flow of DIS

Primary Criteria (Equitable Regional Distribution) Region CAR 25 km Region II 5 km Region VII (Cebu) 11 km Region VIII (Samar) 3 km Region VIII (Leyte) 7 km Region X 7 km Region XI 3 km Total 61 km

Secondary Criteria All concerned DEOs conducting preliminary inventory survey shall be selected

Third Criteria Priority sections recommended by DEO

Most disaster types shall be surveyed in each section All of the disaster types shall be surveyed




Table 5.5 Selected Length of PIS and DIS

Region PIS Section length (km) DIS Section length (km) DIS/PIS length (%) Region CAR 140 25 18

Region II 12 5 41

Region VII (Cebu) 73 11 15

Region VIII(Samaur) 16 3 19

Region VIII(Layrte) 23 7 30

Region X 38 7 18

Region XI 30 3 10

Total 332 61 18

Table 5.6 Selected Road Sections for Detailed Inventory Survey

PIS DIS Region

Road Sections Section Length km

Section Lengthkm

No. of Slopes

DEO in Charge

Road Classification

AADT Disaster

Type

241-244 3 241-244 3 10 Baguio City Kennon Rd

214-241 27 227-234 7 32 Benguet 1st

S 6,880/ 5,014

SC, RC, RE, DF, RS

Baguio- Bontoc Rd [Halsema Highway] 263-341 78 275-280 5 43 Benguet

2nd

A(OT) 953 SC, RC, LS, RE, DF, RS

Nueva Vizcaya- Ifugao-Mt Province Rd [ Lagawe - Banaue]

301-333 32 301-306318-323 10 33 Ifugao

S 275/ 3,116 SC, RC,

LS, DF, RS

CA

R

Subtotal 140 25 118

Daang Maharlika (LZ) [ Dalton Pass ] 208-220 12 208-213 5 27

Nueva Vizcaya Sub

A(NE) 3,769 SC, RC, RS, DF, RE

II

Subtotal 12 5 27 5-30 25 27-30 3 19 Cebu City Cebu- Balamban

Transcentral Highway 30-42 12 33-37 4 28 Cebu 3rd A(EW) 1,001/

1,305 SC, RC, RS, DF

Toledo-Baliri-Santander Rd [ Ginatilan- Alegria ]

143-179 36 172-176 4 4 Cebu 4th A(NS) 500/

12,000 SC, RC, RE, CE, RS

VII

Subtotal 73 11 51 Wright-Taft-Borongan Rd 843-859 16 844-847 3 13 Samar 2nd A(EW) 500/

1,374 SC, RC, RS, DF

995-1003 8 1000-1003 3 9 Leyte 5th Daang Maharlika (LT) [ Mahaplag- Sugod ] 1003- 1018 15 1003-1007 4 26 Southern

Leyte

A(NS)

659/ 1,581

SC, RC, LS, RE, RS, DF

VIII

Subtotal 39 10 48 Sayre Highway [ Misamis Oriental - Bukidnon - Agusan Road ]

1428-1464 36 1444-1449 5 33 Bukidnon 3rd

A(NS) 3,421 SC, RC, RS, RE

Bukidnon - Davao City Rd 1605-1607 2 1605-1607 2 9 Bukidnon

2nd A(NS) 3,340 SC, RC,

RS

X

Subtotal 38 7 42

Davao - Cotabato Rd 1525-1555 30 1532-1535 3 4 Davao-del Sur 1st

A(NS) 3,486/ 6,517

SC, RS, RE

XI

Subtotal 30 3 4 Total Length (km) 332 61 290

Disaster Types; SC: Soils Slope Collapse; RC: Rock Slope Collapse; LS: Landslide; RS: Road Slip; DF: Debris Flow; RE: River Erosion; CE: Coastal Erosion; Road Classification; A(NS) Arterial (North-South Backbone), A(EW): Arterial (East-West Lateral), A(OT): Arterial (Other Road of Strategic Importance), S: Secondary National Road,




5.2.2 Experimental Detailed Inventory Survey

Experimental Detailed Inventory Surveys (DIS) were conducted in Region VII and Region CAR in October 2006 with the purpose of reviewing DIS technique. The said experimental DIS were executed as a collaborative activity involving the Study Team, the Counterpart Team, and the staff of the DEO concerned. The DIS procedure has been improved through this activity.

Table 5.7 Experimental Detailed Inventory Survey Region Road Station Disaster Type Responsible

DEO Execution Date

32 km 939 m 33 km 035 m

RC: Rock Slope Collapse

Cebu- Balamban Transcentral

36 km 945 m 37 km 058 m

SC: Soil Slope Collapse

Cebu 3rd

17 OCT 2006

170 km 710 m 170 km 867 m 171 km 624 m 171 km 664 m

Toledo-Baliri-Santander Rd (Ginatilan- Alegria)

171 km 960 m 172 km 066 m

CE: Coastal Erosion Cebu 4th 18 OCT 2006

VII

Cebu- Balamban Transcentral

32 km 846 m 32 km 906 m

SC: Soil Slope Collapse

Cebu City 19 OCT 2006

215 km 130 m 215 km 200 m

RE: River Erosion Benguet 1st CAR Kennon Rd 241 km 50 m

241 km 80 m SC: Soil Slope Collapse

Baguio City

25 OCT 2006

5.2.3 Results of the Detailed Inventory Survey

(1) Summary Results of the DIS are summarized in Table 5.9.

Of the total length of 61 km of planned DIS, the surveys of the 10 km sections in Region X and Region XI were not completed by the 20th of Feb 2007. DIS in Regions X and XI will be subsequently conducted by the Counterpart Team and ROs and DEOs of Region X and XI. In

this summary, countermeasure alternatives are set in Table 5.8.

Table 5.8 Countermeasure Alternative Policy Alternative Effectiveness Risk Reduction Ratio

Alternative-I High Effectiveness: Permanent countermeasures to prevent disasters 0.7-1.0 (70%-100%)

Alternative-II Moderate Effectiveness: Mitigating the disasters to some extent 0.3– 0.7 (30%- 70%)

Alternative-III Low Effectiveness: Limited treatment 0.0-0.3 (0-30%)

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RATION

Table 5.9 Result of Detailed Inventory Survey




(2) Example of DIS Results 1) Soil Slope Collapse As an example, the DIS results for Cebu-Balamban Transcentral Highway (29 km 714m-839m) for Soil Slope Collapse are shown in Figure 5.17 to 5.22

Considering field conditions, the countermeasure alternatives were planned as summarized in Table 5.10.

Based on the outputs from Sheets 1 to 4, an indicative feasibility assessment was undertaken, as shown in Figure 5.22.

Table 5.10 Example of Countermeasure Alternative Planning for Soil Slope Collapse

Alternative Effectiveness Risk Reduction Ratio

Alternative-I

High Effectiveness: Permanent countermeasures to prevent disasters

- Shotcrete - Concrete Retaining Wall

0.9

Alternative-II

Moderate Effectiveness: Mitigating the disasters to some extent

- Grouted Riprap Retaining Wall

0.6

Alternative-III Low Effectiveness: Limited treatment

-Vegetation/Tree Planting 0.3

Figure 5.17 General View of Example DIS Slope for Soil Slope Collapse




Figure 5.18 Example of Inventory Sheet 3: Sketches for Soil Slope Collapse




Figure 5.19 Example of Inventory Sheet 4-1: Planning of Countermeasure Alternative I for Soil Slope Collapse




Figure 5.20 Example of Inventory Sheet 4-2: Planning of Countermeasure Alternative II for Soil Slope Collapse




Figure 5.21 Example of Inventory Sheet 4-3: Planning of Countermeasure Alternative III for Soil Slope Collapse




Figure 5.22 Example of Inventory Sheet 5: Indicative Feasibility Assessment for Soil Slope Collapse

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CHAPTER 5 RESULTS OF PILOT INVENTORY SURVEY